Failure analysis and durability of preinsulating district heat pipes

Abstract

In this work, surface analysis and failure of rigid polyurethane (PUR) near to the metal interface of an insulating district heat pipe were evaluated. The hybrid composite consists of a steel tube surrounded by a rigid and thick PUR layer for thermal isolation. Accurate life spam approximation of district heat pipes based on PUR and steel is a complex task because of a number of variables involved in the service life of the composite, such as corrosion on the metal pipe, unexpected variations in humidity and temperature, and the quality of raw materials. In this work, artificial aging, mechanical tests, thermogravimetric, and surface analysis were conducted to determine the failure mechanisms at the polymer-metal interface. From thermogravimetric data, different methods were applied to identify parameters of the kinetics of solid decomposition, and subsequently, the lifetime of the product was estimated. From the methods evaluated, the Chang analysis gave the best approach when compared to results attained by mechanical tests and predictions established by the standard EN 253.

Effect of a thermal treatment on thermoplastic polyurethane– metal hybrids

“…TPEs reduce also shock and vibration, contribute to electrical insulation, and additionally offer a high resistance to wear and abrasion. 4 Steel is also a common substrate in polymer-metal composites; 5,6 it is still one of the most used metals in the industry due to its excellent mechanical performance and versatility in adjusting mechanical properties to specific engineering applications. 7 There are several technologies for joining polymers to metal substrates such as mechanical interlocking, adhesive bonding, and plastic overmolding processes.…”